Instance create fails with "no host found" during schedule due to diskfilter filters hosts out

Issue

During scheduling the diskfilter filters out e.g. compute4 as it says it only has ~9GB available disk (instance requested 32GB)

2017-09-06 22:45:02.517 666974 DEBUG nova.scheduler.filters.disk_filter [req-a2f9c5bd-be00-45d9-bb4d-d18b7b1c158c 0935402132ad46958c43b49876a190ae fc70a52dee4f455ba1e0587f32d9116e - - -] (compute4.localdomain, compute4.localdomain) ram: 367074MB disk: 9216MB io_ops: 0 instances: 0 does not have 32768 MB usable disk, it only has 9216.0 MB usable disk. host_passes /usr/lib/python2.7/site-packages/nova/scheduler/filters/disk_filter.py:68

From what the compute reports it should be ~64GB available:

• At about 2017-09-06 22:43 we see that the compute reported 744GB (total) and 680GB (used) which matches the ~~64GB available disk:

2017-09-06 22:43:25.861 430718 INFO nova.compute.resource_tracker [req-ab766b51-07fa-4930-bc6c-6ccff8cac2f6 - - - - -] Final resource view: name=compute4.localdomain phys_ram=786338MB used_ram=419264MB phys_disk=744GB used_disk=680GB total_vcpus=88 used_vcpus=95 pci_stats=[]
2017-09-06 22:44:26.689 430718 INFO nova.compute.resource_tracker [req-ab766b51-07fa-4930-bc6c-6ccff8cac2f6 - - - - -] Final resource view: name=compute4.localdomain phys_ram=786338MB used_ram=419264MB phys_disk=744GB used_disk=680GB total_vcpus=88 used_vcpus=95 pci_stats=[]
2017-09-06 22:45:26.228 430718 INFO nova.compute.resource_tracker [req-ab766b51-07fa-4930-bc6c-6ccff8cac2f6 - - - - -] Final resource view: name=compute4.localdomain phys_ram=786338MB used_ram=419264MB phys_disk=744GB used_disk=680GB total_vcpus=88 used_vcpus=95 pci_stats=[]
2017-09-06 22:46:26.909 430718 INFO nova.compute.resource_tracker [req-ab766b51-07fa-4930-bc6c-6ccff8cac2f6 - - - - -] Final resource view: name=compute4.localdomain phys_ram=786338MB used_ram=419264MB phys_disk=744GB used_disk=680GB total_vcpus=88 used_vcpus=95 pci_stats=[]
2017-09-06 22:47:27.485 430718 INFO nova.compute.resource_tracker [req-ab766b51-07fa-4930-bc6c-6ccff8cac2f6 - - - - -] Final resource view: name=compute4.localdomain phys_ram=786338MB used_ram=419264MB phys_disk=744GB used_disk=680GB total_vcpus=88 used_vcpus=95 pci_stats=[]
2017-09-06 22:48:27.004 430718 INFO nova.compute.resource_tracker [req-ab766b51-07fa-4930-bc6c-6ccff8cac2f6 - - - - -] Final resource view: name=compute4.localdomain phys_ram=786338MB used_ram=419264MB phys_disk=744GB used_disk=680GB total_vcpus=88 used_vcpus=95 pci_stats=[]

No disk_allocation_ratio is configured in nova.conf on controllers/computes:

#reserved_host_disk_mb=0
#disk_allocation_ratio=0.0